醋酸乙烯酯种子乳液聚合动力学研究

用装有红外跟踪器和计算机记录监控系统的膨胀计进行了醋酸乙烯酯的种子乳液聚合。聚合直接从乳液聚合的阶段Ⅱ开始，避开了复杂的成核阶段和成核阶段粒度变化对动力学参数的影响。在引发剂浓度５．０３０×１０＾－５￣１．００２×１０＾－３ｍｏｌ／Ｌ范围内，依据转化率随时间的变化关系，求出了准稳态聚合速率、自由基进入乳胶粒子的速率、自由基从乳胶粒子解吸的速率和ｋｐｎ＾－。结果表明：聚合速率、自由基进入乳胶粒子的速     

Regioselective Michael-induced cyclisation of γ- and δ-hydroxy vinyl sulfides and vinyl dithiocarbamates

We herein describe the unprecedented use of heteroaryl vinyl sulfides and vinyl dithiocarbamates as hetero-Michael addition acceptors. Combined chelating and electron-withdrawing effects are postulated to stabilise the transient anionic species and allow smooth Michael-induced ring closure to produce diversely functionalised C-glycosides.     

A statistical approach to characterize the viscoelastic creep compliances of a vinyl ester polymer

The objective of this study was to develop a model to predict the viscoelastic material functions of a vinyl ester (VE) polymer with variations in its experimentally obtained material properties under combined isothermal and mechanical loading. Short-term tensile creep experiments were conducted at three temperatures below the glass transition temperature of the VE polymer, with 10 replicates for each test configuration. The measured creep strain versus time responses were used to determine the creep compliances using the generalized viscoelastic constitutive equation with a Prony series representation. The variation in the creep compliances of a VE polymer was described by formulating the probability density functions (PDFs) and the corresponding cumulative distribution functions (CDFs) of the creep compliances using a two-parameter Weibull distribution. Both Weibull scale and shape parameters of the creep compliance distributions were shown to be time and temperature dependent. Two-dimensional quadratic Lagrange interpolation functions were used to characterize the Weibull parameters to obtain the PDFs and, subsequently, the CDFs of the creep compliances for the complete design temperature range during steady state creep. At each test temperature, creep compliance curves were obtained for constant CDF values and compared with the experimental data. The predicted creep compliances of the selected VE polymer in the design space are in good agreement with the experimental data for all three test temperatures.     

Iodoolefinic polypropionate building blocks from vinyl silanes with control of geometry by solvent and by neighboring group participation

Iododesilylation of trisubstituted (Z)-silyl olefins proceeds with retention of geometry in hexafluoroisopropanol (HFIP) but, for unhindered cases, with inversion of geometry in DMSO. When an acyloxy substituent is positioned to participate in the reaction, the protocol consistently leads to inversion of geometry.     

15-[(Z)-Phenylmethylidene]-7,14-dioxadispiro[5.1.5.2]pentadecanes: stereoselective one-pot assembly from cyclohexanones and phenylacetylene in a KOH/DMSO suspension

Cyclohexanones react with phenylacetylene in a KOH/DMSO suspension (80 °C, 1 h) to give unexpectedly phenylmethylidene dispirocyclic ketals, 15-[(Z)-phenylmethylidene]-7,14-dioxadispiro[5.1.5.2]pentadecanes, in 16-22% yields (along with the anticipated β,γ- and α,β-ethylenic ketones).     

Synthesis,NMR‐Spectroscopy,and Molecular Structure of a Phosphonyl Ene Diamine

First examples of ene diamines with a phosphonate function at the C=C double bond were obtained by the reaction of dialkyl H‐phosphonates with bis(N‐tert‐butyl)‐diimine derived from glyoxal, [1,4‐bis(tert‐butyl)‐1,4‐diaza‐1,3‐butadiene], and isolated as hydrochlorides. Preferentially the cis‐diamine is formed. The new phosphonates are characterized by multinuclear NMR spectroscopy(¹H, ¹³C, ³¹P). In addition the methyl ester 8a was characterized by ^14,15N NMR spectroscopy as well as by several 2D NMR techniques and single‐crystal X‐ray diffraction, unequivocally establishing the ene diamine structure. In the crystal dimers of the cations are formed by P–O ··· H–N hydrogen bonding.     

Nickel and cationic palladium complexes bearing (imino)pyridyl alcohol ligands: Synthesis, characterization and vinyl polymerization of norbornene

A series of nickel and palladium complexes bearing (imino)pyridyl alcohol tridentate [N,N,O] ligands, 2-(ArNCMe)-6-{(HO)CR₂}C₅H₃N (L1-L4), were synthesized and sufficiently characterized by elemental and spectroscopic analysis along with X-ray diffraction analysis. The X-ray diffraction demonstrated that five-coordinated nickel halide complexes (1a-4a and 1b) and six-coordinated nickel acetate complex (1c) were prepared, and cationic palladium complexes (1d and 2d) formed with the [PdCl₄]²⁻ counterion. All these complexes displayed high catalytic activities up to 1.883 × 10⁷ g(PNB) mol⁻¹(cat) h⁻¹ (2d) for the vinyl polymerization of norbornene on treatment with excess methylaluminoxane (MAO), affording the vinyl-type PNBs with high molecular weights and relatively narrow molecular weight distributions. The parameters of reaction conditions, the type of metals and steric effects of coordinative ligands had influences on the catalytic properties.     

Electrochemical, EPR and computational results on [Fe2Cp2(CO)2]-based complexes with a bridging hydrocarbyl ligand

The dimetallacyclopentenone complexes [Fe₂Cp₂(CO)(μ−CO){μ−η¹:η³−C_αHC_β(R)C(O)}] (R = CH₂OH, 1a; R = CMe₂OH, 1b; R = Ph, 1c) were prepared by photolytic reaction of [Fe₂Cp₂(CO)₄] with alkyne according to the literature procedure. The X-ray and the electrochemical characterization of 1c are presented. The μ-allenyl compound [Fe₂Cp₂(CO)₂(μ−CO){μ−η¹:η²_α,β−C_αHC_βCMe₂][BF₄] ([2][BF₄]), obtained by reaction of 1b with HBF₄, underwent monoelectron reduction to give a radical species which was detected by EPR at room temperature. The EPR signal has been assigned to [Fe₂Cp₂(CO)₂(μ−CO){μ−η¹:η²_α,β-C_αHC_βCMe₂}], [2]^•. The molecular structures of [2]⁺ and [2]^• were optimized by DFT calculations. The unpaired electron in [2]^• is localized mainly at the metal centers and, coherently, [2]^• does not undergo carbon-carbon dimerization, by contrast with what previously observed for the μ-vinyl radical complex [Fe₂Cp₂(CO)₂(μ−CO){μ−η¹:η²-CHCH(Ph)}]^•, [3]^•. Electron spin density distributions similar to the one of [2]^• were found for the μ-allenyl radical complexes [Fe₂Cp₂(CO)₂(μ-CO){μ-η¹:η²_α,β-C_αHC_βC(R¹)(R²)}]^• (R¹ = R² = H, [4]^•; R¹ = H, R² = Ph, [5]^•; R¹ = R² = Ph, [6]^•).     

Influence of Vinyl Groups on the UV-Visible Spectra and Self-Dimerization of Pyrromethenones

Spectral analyses of vinylneoxantho- and vinylisoneoxanthobilirubic acid methyl esters, with endo and exo-vinyl groups respectively, show that the exo-vinyl group causes (1) a greater bathochromic and hyperchromic shift of the long wavelength UV-vis absorption and (2) a smaller dimer association constant in CDCl₃ than does the endo-vinyl in these pyrromethenones.     

Rh(I)-catalyzed intramolecular hetero-[4+2] cycloaddition of ω-alkynyl-vinyl oximes

Cationic rhodium(I) catalyst derived from [RhCl(cod)]₂ and AgSbF₆ in hexafluoroisopropanol (HFIP) efficiently catalyzed the formation of bicyclic pyridine derivatives by intramolecular hetero-[4+2] cycloadditions of ω-alkynyl-vinyl oximes.